There is known an electromagnetic wave emission device that emits electromagnetic waves to plasma (see JP 2007-113570A). The electromagnetic wave emission device that is described in JP 2007-113570A equips an ignition device that generates a plasma discharge by emitting microwave to a combustion chamber prior to or after the ignition of air-fuel mixture. The ignition device generates a local plasma using discharge of a spark plug so that the plasma is generated in the high-pressure environment, and enhances this plasma using microwave. The local plasma is generated at a discharge gap between a ground terminal part and a tip part of an anode terminal.